The 27-year-old spent the 2013-14 season on loan at the Bundesliga club, making 24 league appearances, and has now made the move permanent.

Djourou joined Arsenal in 2003 as a 16-year-old and made 144 appearances for the first team, though he struggled to nail down a spot in Arsene Wenger's starting XI in recent seasons, also spending the second half of the 2012-13 season on loan in Germany, with Hannover 96.

The versatile defender, who featured at both centre-back and right-back throughout his Gunners career, represented Switzerland at the World Cup and will hope to help Hamburg improve on last season's 16th-placed finish in 2014-15.